Fixing Error CS0234: The type or namespace name 'Ajax' does not exist in the namespace 'System.Web.Mvc'

Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2014/10/27/fixing-error-cs0234-the-type-or-namespace-name-ajax-does.aspx

In the process of reviewing the excellent book ‘Expert ASP.NET Web API 2 for MVC Developers’ by Adam Freeman, some of the examples failed with the following:

Compiler Error Message: CS0234: The type or namespace name 'Ajax' does not exist in the namespace 'System.Web.Mvc' (are you missing an assembly reference?)

1. Stopping the project
2. Changing the Copy Local property against System.Web.Mvc from False to True.
3. Restart and it now works!